Buggy code:
public class HttpHeaders implements MultiValueMap < String , String > { private static final String ACCEPT = "Accept" ; private static final String ACCEPT_CHARSET = "Accept-Charset" ; private static final String ALLOW = "Allow" ; private static final String CACHE_CONTROL = "Cache-Control" ; private static final String CONTENT_LENGTH = "Content-Length" ; private static final String CONTENT_TYPE = "Content-Type" ; private static final String DATE = "Date" ; private static final String ETAG = "ETag" ; private static final String EXPIRES = "Expires" ; private static final String IF_MODIFIED_SINCE = "If-Modified-Since" ; private static final String IF_NONE_MATCH = "If-None-Match" ; private static final String LAST_MODIFIED = "Last-Modified" ; private static final String LOCATION = "Location" ; private static final String PRAGMA = "Pragma" ; private static final String [ ] DATE_FORMATS = new String [ ] { "EEE,<seq2seq4repair_space>dd<seq2seq4repair_space>MMM<seq2seq4repair_space>yyyy<seq2seq4repair_space>HH:mm:ss<seq2seq4repair_space>zzz" , "EEE,<seq2seq4repair_space>dd-MMM-yy<seq2seq4repair_space>HH:mm:ss<seq2seq4repair_space>zzz" , "EEE<seq2seq4repair_space>MMM<seq2seq4repair_space>dd<seq2seq4repair_space>HH:mm:ss<seq2seq4repair_space>yyyy" } ; private static TimeZone GMT = TimeZone . getTimeZone ( "GMT" ) ; private final Map < String , List < String > > headers = new org . springframework . util . LinkedCaseInsensitiveMap < List < String > > ( 8 ) ; public void setAccept ( List < MediaType > acceptableMediaTypes ) { } public List < MediaType > getAccept ( ) { } public void setAcceptCharset ( List < Charset > acceptableCharsets ) { } public List < Charset > getAcceptCharset ( ) { } public void setAllow ( Set < HttpMethod > allowedMethods ) { } public Set < HttpMethod > getAllow ( ) { } public void setCacheControl ( String cacheControl ) { } public String getCacheControl ( ) { } public void setContentLength ( long contentLength ) { } public long getContentLength ( ) { } public void setContentType ( MediaType mediaType ) { } public MediaType getContentType ( ) { } public void setDate ( long date ) { } public long getDate ( ) { } public void setETag ( String eTag ) { } public String getETag ( ) { } public void setExpires ( long expires ) { } public long getExpires ( ) { } public void setIfModifiedSince ( long ifModifiedSince ) { } public long getIfNotModifiedSince ( ) { } public void setIfNoneMatch ( String ifNoneMatch ) { } public void setIfNoneMatch ( List < String > ifNoneMatchList ) { } public List < String > getIfNoneMatch ( ) { } public void setLastModified ( long lastModified ) { } public long getLastModified ( ) { } public void setLocation ( URI location ) { } public URI getLocation ( ) { } public void setPragma ( String pragma ) { } public String getPragma ( ) { } private String quote ( String s ) { } private String unquote ( String s ) { } private long getFirstDate ( String headerName ) { } private void setDate ( String headerName , long date ) { <START_BUG> SimpleDateFormat dateFormat = new SimpleDateFormat ( HttpHeaders . DATE_FORMATS [ 0 ] ) ; <END_BUG> dateFormat . setTimeZone ( HttpHeaders . GMT ) ; set ( headerName , dateFormat . format ( new Date ( date ) ) ) ; } public String getFirst ( String headerName ) { } public void add ( String headerName , String headerValue ) { } public void set ( String headerName , String headerValue ) { } public void setAll ( Map < String , String > values ) { } public Map < String , String > toSingleValueMap ( ) { } public int size ( ) { } public boolean isEmpty ( ) { } public boolean containsKey ( Object key ) { } public boolean containsValue ( Object value ) { } public List < String > get ( Object key ) { } public List < String > put ( String key , List < String > value ) { } public List < String > remove ( Object key ) { } public void putAll ( Map < ? extends String , ? extends List < String > > m ) { } public void clear ( ) { } public Set < String > keySet ( ) { } public Collection < List < String > > values ( ) { } public Set < Entry < String , List < String > > > entrySet ( ) { } @ Override public boolean equals ( Object other ) { } @ Override public int hashCode ( ) { } @ Override public String toString ( ) { } }

Fix:
SimpleDateFormat dateFormat = new SimpleDateFormat ( HttpHeaders . DATE_FORMATS [ 0 ] , Locale . US ) ;